Kulik, A., A. Zaderihin, V. Shulgin, and A. Martynenko. “INDICATORS OF HEART RATE VARIABILITY IN HEALTHY VOLUNTEERS DEPENDING ON THE RESPIRATION RATE AND INHALATION-EXHALATION RATIO”. The Journal of V. N. Karazin Kharkiv National University, Series "Medicine", no. 18, 1, pp. 14-19, https://periodicals.karazin.ua/medicine/article/view/6950.